The burner apparatus described above is used as a burner apparatus for a gas turbine engine used in a co-generation system or a burner apparatus used for an incinerator. With this burner apparatus, it is necessary not only to adjust the flow amounts of the fuel gas to be fed to the main combustion channel and the pilot combustion channel in accordance with increase/decrease in the combustion load for assuring good combustion with maintaining appropriate equivalent ratio for the main combustion channel and the pilot combustion channel, but also to adjust the flow amounts of the air to be fed to the main combustion channel and the pilot combustion channel.
Conventionally, in order to make the adjustment of the flow amounts of the fuel gas to the main combustion channel and the pilot combustion channel, a flow-amount adjusting valve was provided in a fuel gas supply line to the main combustion channel and in a further fuel gas supply line to the pilot combustion channel, respectively, so as to make the adjustment of the flow amounts of the fuel gas to the main combustion channel and to the pilot combustion channel, independently of each other.
However, according to the prior art described above, as the adjustment of the supply amount of fuel gas to the first channel and that to the second channel in accordance with the combustion load are effected independently of each other, the adjustment operation was troublesome.
Further, in the case of the burner apparatus of the above type which effects pilot combustion and main combustion, the supply amounts of fuel gas respectively to the main combustion channel and to the pilot combustion channel are reduced in association with decrease in the combustion load relative to a rated combustion load. In association with such decrease in the supply amount, it is necessary to increase the supply amount to the pilot combustion channel to maintain stable pilot combustion.
Moreover, with such burner apparatus, it is especially needed to mix fuel gas and air in a reliable manner inside the first channel in which the main combustion is effected. For, if they are not mixed well, there occurs unevenness in the equivalent ratio in the fuel-air mixture containing the fuel gas and the air in a mixed state, so that in a region of a higher equivalent ratio high-temperature combustion will occur, resulting in increase in NOx generation amount.
According to the conventional burner apparatus, as shown in FIG. 44, a supply line provided within the combustion channel for receiving fuel gas supply defines a plurality of supply openings arranged in dispersion for discharging the fuel gas through the plural openings to the combustion channel. In this case, the plural supply openings are opened on the downstream side in the direction of air flow in the combustion channel, so as to discharge the fuel gas in the same direction as the air. With this construction, by dispersing the supply of fuel gas to the combustion channel, the apparatus was designed to improve the mixing degree between the air and the fuel gas G.
With such conventional burner apparatus, in order to achieve uniformity in the supply of fuel gas to the combustion channel by providing a plurality of supply openings for one supply line, it is desirable for the supply openings to be provided as many as possible. However, as the total amount of fuel gas to be supplied to the combustion channel is determined in advance, as the number of the supply openings is increased, it becomes necessary to reduce the opening area of each supply opening.
As a result, there occurs increased pressure loss at the supply openings. Then, in order to discharge a predetermined amount of the fuel gas, it becomes necessary to supply the fuel gas with an increased pressure into the supply line, thus requiring disadvantageous physical and capacity enlargement of the gas supplying means for the burner apparatus.
Incidentally, the equivalent ratio represents an amount indicative of concentration aspect of the fuel-air mixture of the fuel and the combustion air and this is defined herein as follows.equivalent ratio=(fuel concentration/air concentration)/(fuel concentration/air concentration)st 
Each concentration is represented in the mole value, and (fuel concentration/air concentration)st is a theoretical fuel-air ratio. This theoretical fuel-air ratio is the concentration ratio between an amount of fuel and air needed for complete oxidation of that amount of fuel.